A conventional transition from a waveguide to a stripline is described in a textbook by Reinmund Hoffmann, Integrierte Mikrowellenschaltung (Integrated Microwave Circuitry), Springer-Verlag 1983, pages 90, 91. As disclosed in this publication, the stepped ridge, which in bonded to the stripline, has a rectangular cross section and is mounted as a separate part in the waveguide. From the aspect of manufacturing technology, this conventional transition from a waveguide to a stripline is relatively costly.
In a transition from a waveguide to a stripline described in Japan Patent No. 05 090807, a ridge having a change in height which is continuous in stages is arranged in the waveguide. The cross-sectional shape of the ridge tapers perpendicularly to the longitudinal axis of the waveguide.
A transition from a waveguide to a stripline is described in French Patent No. 69 008 in which a stepped ridge in the waveguide has a rectangular cross section. This form of the ridge makes manufacturing difficult, particularly if the waveguide is to be one piece with the ridge.